Abstract

Flutter prediction methods for aeroengine fans at present typically combine a complex aerodynamic analysis with a simple model of the mechanical behavior of the fan. In this paper a more sophisticated model of the mechanical response is used to investigate flutter and provide additional insight into the physical mechanisms involved. The model incorporates twin orthogonal modes, which are two independent vibration patterns similar in shape and resonant frequency but displaced 1/4 wave circumferentially in space. Flutter can be thought of as a self excited vibration in which the response of each blade in one mode generates aerodynamic forces on the blades which drive the twin mode—and vice versa. The flutter frequency can be determined by considering the phasing between the twin modes; whether flutter does actually occur (at this frequency) depends upon the relationship between the aerodynamic force coefficients and the amplitude response of each mode. The greatest tendency to flutter occurs when the twin modes are identical in frequency. For the more practical case of a frequency split between the modes the tendency to flutter decreases with increased frequency separation, and the vibration pattern becomes non-uniform. The non-uniformities include unequal blade amplitudes, unequal interblade phase angles, variation from blade to blade in the temporal phase between twist and flap within each individual blade, and a deflected shape which is not sinusoidal circumferentially.

Copyright in the material you requested is held by the American Society of Mechanical Engineers (unless otherwise noted). This email ability is provided as a courtesy, and by using it you agree that you are requesting the material solely for personal, non-commercial use, and that it is subject to the American Society of Mechanical Engineers' Terms of Use. The information provided in order to email this topic will not be used to send unsolicited email, nor will it be furnished to third parties. Please refer to the American Society of Mechanical Engineers' Privacy Policy for further information.

Shibboleth is an access management service that provides single sign-on protected resources.
It replaces the multiple user names and passwords necessary to access subscription-based content with a single user name and password that can be entered once per session.
It operates independently of a user's location or IP address.
If your institution uses Shibboleth authentication, please contact your site administrator to receive your user name and password.